1、 1 Design based on HDB3 encoder of EDA technology and realizing Summary HDB3 yard is one of the important components in digital baseband communication system, because it does not have direct-flow compositions, it is strong to examine the ability by mistake, have advantages such as performance of clo
2、ck recovery, etc, recommend the baseband that uses to transmit one of the yard types as ITU. Have introduced principle and method of HDB3 code at first, has proposed a method based on HDB3 encoder of EDA technology, have simple, with low costs circuit, development period is short, it is high to carr
3、y out the speed, upgrade characteristics such as convenience, etc. Foreword Third-order high-density bipolar code is an important serial data transmission encoding, digital communication is an important part of the system. And the most common NRZ code, compared, HDB3 code has many advantages, such a
4、s: eliminating the DC component NRZ code with clock recovery and better anti-jamming performance, making it more suitable for long-distance channel transmission. At the same time, HDB3 error detection code has a strong ability to use HDB3 code when the data transfer sequence, if a single bit error o
5、ccurs during transmission, the law of alternating polarity will be destroyed, so the receiver HDB3 code based on the unique law characteristics, can be detected the error and correct the error, and facilitate the extraction of HDB3 code bit timing information. HDB3 code as data transmission and thus
6、 a pattern, widely used, as ITU recommended pattern one. HDB3 coding performed by the realization of a variety of ways, the common solution is application-specific transceiver chip HDB3, such as the selection of specific E1 transceiver and MCU DS2153Q the conversion of the code system. This article
7、provides a the use of modern EDA technology to ACEX series FPGA chip EPlK10 for the hardware platform for the Quartus II software platform to VHDL, for the development of tools for FPGA implementation of the HDB3 encoder design. HDB3 yard High Density Bip01ar Code of three codes, a pair of polarity
8、yard of high density for three steps It is an important code way of serial data transmission, it is one of the important components in the digital communication system too. And most frequently used NRZ yard Non-Return Zero, does not return zero yard Compare, HDB3 yard has a lot of advantages, for ex
9、ample: Dispel NRZ direct-flow composition of yard, have clock recovery 2 and better interference-free performance, this makes it suitable for the channel of long distance to transmit. Meanwhile, HDB3 yard has more strongly examining the ability by mistake, when the data array is transmitted with HDB
10、3 yard, if present yard singly by mistake in the transmission course, its polarity will change the law alternatively and will be destroyed, therefore is receiving the end according to one yard of this unique law characteristics of HDB3, can examine and make mistakes and correct the mistake, one yard
11、 of convenience of HDB3 drew the regular information in the location at the same time. Therefore one yard of a kind of code types as data transmission of HDB3, it is extensive to employ, become one of the yard types that ITU recommends using. There are multiple channels in the realization of HDB3 on
12、e yard of compiled code devices, commonly used solutions are to employ specialized HDB3 to receive and dispatch the chip, specialized E1 receives and dispatches chip DS2153Q and one-chip computer and realizes this yard of conversion function made such as selecting for use. This text offers one kind
13、to utilize modern EDA technology, regard ACEX series FPGA chip EPlK10 as the hardware platform, regard Quartus II as the software platform, with VHDL, it is a developing instrument, the design plan of HDB3 encoder that suitable FPGA realizes. 1 Code rule of HDB3 yard The code rule of HDB3 yard is as
14、 follows: （ 1） Vary the news code into AMI yard； AMI yard Alternate Mark Inversion Full name to spread number, overturn yard alternatively. This one kind encodes code 0 and 1 of news according to the following rule: Last yard 0 code 0 still, and at code if you cant turn into, transmit alternative by
15、 that yard to 1 1, -1, 1, -l； （ 2） Check the intersection of AMI and connecting 0 situation with in the yard, as 4 or more of having connect 0 bunches with, keep the form of AMI not changing； Appear 4 or more connect 0 with, 0 turn 4th after the 1 into until the first one the intersection of O and y
16、ard With the symbol of polarity, show n is own is V, it is V n is own with V； （ 3） Check whether not 0 yards of numbers among adjacent v yard is an even number, if is the even number, again present V yard the first one the first 0 yard later turn by B yard B into for 0 times, and is a the first one
17、is the polarities of yard opposite of O the polarities of B, and make not 0 yards behind begin to replace the change from V yard. NRZ one yard of course changed into HDB3 yard such as Table 1 shown for example. 3 2 Modeling and realizing of HDB3 encoder Go on data that encode according to encode the
18、 principle to convert to AMI yard first while being above-mentioned directly, then go on, add the intersection of V and yard, add the intersection of B and yard, operate, will find, transform the intersection of AMI and yards of one the 1 occasionally into one 1 Yards of course that polarity form, b
19、ut after adding B yard and operating, only if zero yuans of corresponding polarity might overturn, so there are two pieces of course that signal polarity produces. Analyze the code result of HDB3: V positive to shoulder not alternative in polarity of yard, remaining 1 and the intersection of B and y
20、ard regard as until an organic whole positive to shoulder not alternative too, meet the intersection of V and polarity with the intersection of zero and identical polarity of in the front of yard at the same time. Therefore has produced the thinking that use FPGA carries on HDB3 one yard of codes: G
21、o on and add V yard first, adds B yard and operates, in this course, wouldnt consider its polarity, then the intersection of V and yard, 1 divide two into with the intersection of B and yard, carry on polar variety come on one realize respectively. So can raise the efficiency of the system, the decr
22、ease system delays time at the same time. The digital circuit part of HDB3 encoder is made up of three pieces of module: V yard produced the unit V Gen ,B yard produced the unit B Gen ,A pair of polar conversion units single2double of single polarity ,Their structure charts. 2. 1 V yard produced the
23、 unit V_Gen V one yard of functions of producing the unit is to connect four in the news code with 0 bunches of detection in fact, namely when connecting with 0 bunches four, vary, succeed V yard fourth 0, but otherwise, keep the former state of the news code exporting. For offer the convenience to
24、encoding the course, transmit yard, say with 2 binary scale one the intersection of code and yuan in the original signal, while going on with V yard, use11 in unison Annotate it, original l yard uses 01 Annotate, 0 yards use 00Annotate. Fig. 2 shows for V one yard of job flow diagrams which produces
25、 the unit. The original signal NRZ_in produced the unit V_Gen through V yard And then signal V_Gen_out wave form: 2. 2 B yard produced the unit B_Gen B one yard of functions of producing the unit is to guarantee the additional V array after yard is not destroyed Polarity overturns alternatively Direct-flow characteristic does not formed, namely when there are a piece of not 0 yards of even number between adjacent V yard, after one is small for that section if you cant vary as, destroy by symbol a B of yards
